High-precision computer-aided microscope system

ABSTRACT

A microscope frame structure having a front brace for added stability and having a dual plate structure. The front brace is rigidly coupled to the front ends of an upper portion and a base portion. The upper portion then carries optical elements such as a camera for instance. In effect, the optical elements thus reside on a bridge structure, with substantially the same structural support at both ends of the bridge. The arrangement is particularly useful in automated specimen imaging and analysis systems. The dual frame is composed of an upper plate, which supports a sample, a lower plate which contacts an elevating screw, and a spacer post in between the upper plate and lower plate. This configuration allows for more stable movement of samples.

REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional PatentApplication Serial No. 60/064,558, filed Oct. 17, 1997 and to U.S.Provisional Patent Application Serial No. 60/064,559, filed Oct. 20,1997. Moreover, this application is a continuation-in-part of U.S.Patent Application Ser. No. 09/174,140, filed Oct. 16, 1998 and PCTApplication Serial No. PCT/US98/21953 filed Oct. 16, 1998.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention is related generally to the field ofmicroscopy, and more particularly to the configuration of opticalmicroscopes and microscope-based electronic imaging systems.

[0004] 2. Description of the Related Art

[0005] In its most basic form, a microscope typically includes a base, aplate or stage for holding a sample, a magnifier commonly including aseries of lenses, and a viewer for presenting a magnified image to anobserver. The principal purpose of a microscope is to create a magnifiedimage of a sample of a specimen and to accurately present the enlargedimage to an observer or to an electronic imaging apparatus used forimage acquisition, display, measurement, analysis, communication,archiving, or data management.

[0006] Over the years, microscopes have evolved into very complex andsophisticated optical instruments, taking a variety of forms. While mostmicroscopes are manually operable and may present a magnified image forviewing by an operator, one of the most important recent advances inmicroscopy has been the development of automated, computer-aidedmicroscopes. Most computer-aided microscopes include the conventionalelements of manually operated microscopes but are further configured incombination with a digital computer. The computer may serve a variety offunctions, such as, for instance, controlling the position of amotorized stage, controlling the focusing system, or controlling otheroptical components such as microscope objectives.

[0007] In a typical arrangement, a computer-aided microscope systemincludes an electronic photodetector or imaging system such as a videoor CCD camera interconnected to the viewer, with the output from thedetector being fed into a computer processor for a variety of functionsincluding analysis or image enhancement or display. The computerprocessor in turn may provide control signals to the microscope, forinstance, to control the stage position, focus drive or other aspects ofthe system. Provided with this arrangement, a computer-aided microscopemay enable the automatic analysis of a wide variety of objects, such ascytological samples, pathology specimens or semiconductor chips (solidstate devices). Further, the automated analysis may be easily enhancedby appropriate computer programming as well as by the addition ofassorted peripherals (such as data storage devices and interactiveuser-input devices).

[0008] In automated cytology sample analyses, for instance, a specimenis drawn from a patient, a sample is prepared from that specimen, andthe sample is placed into the automated microscope. An image detector(e.g., CCD camera) may electronically scan the sample and therebyreceive digital images of discrete regions of the sample. The detectormay then feed these digital images to a processor, which stores theimages in memory and analyzes the images. In addition, the processor mayreceive from the microscope an indication of the spatial coordinates ofthe stage (e.g., X and Y planar coordinates, and a Z focus coordinate).Through complex image analysis algorithms, the processor may identifycellular matter of interest in the sample and may then mark in memory anindication of the stage position coordinates associated with thatcellular matter. Samples may be deposited on slides with fiducial marksto ensure that the X-Y locations are accurate from microscope tomicroscope or calibration procedures can be developed and used to ensurethat the X-Y coordinates apply from machine to machine.

[0009] In turn, once the processor completes its analysis, it maygenerate a routing function keyed to the stage coordinates and definingan order by which the automated microscope should present areas of thesample to an operator such as a cytotechnologist. Through use of thisrouting function, the computer processor may thus control the microscopestage position and microscope focus, and may thereby present thecellular matter or other objects or optical fields of interest to theoperator through the microscope field of view. In addition, oralternatively, the automated-microscope system may be configured toinclude a computer monitor, which may present the microscopic fields ofview to the operator without requiring the operator to look through themicroscope ocular(s).

[0010] As a general rule, precision, accuracy and speed are critical tothe useful operation of a microscope in addition to the quality (e.g.,resolution) of the optical magnification devices and processes. This isparticularly important for computer-aided microscopy systems. Incytological specimen analysis, for instance, a cytotechnologisttypically needs to be able to locate atypical or abnormal cells inspecimens rapidly, precisely and accurately, since cells are typicallyless than a few hundred microns in their maximum linear dimension. Whilemany cancer-related cytological changes are characteristic and can bedetected and classified with a high degree of accuracy by anappropriately configured microscope, inaccurate or imprecise microscopeconfigurations can be the source of unacceptable false positive or falsenegative cell classifications and sample specimen diagnoses.

[0011] Further, modern vision systems employing computer-aided imageanalysis have imposed on microscopes even more stringent requirementsfor high precision, mechanical stability and optical and illuminationrepeatability. Unfortunately, however, traditional mechanical (e.g.fully manual) microscope systems, as well as many of the currentlyavailable automated microscope systems, have not provided the positionalaccuracy, repeatability, stability and resolution required for reliable,reproducible quantitative microscopic imaging applications.

[0012] To ensure proper operation, for instance, a microscope must be asstable as possible. The microscope must be stable in the presence ofambient vibrations and also stable with respect to internally introducedvibrations. However, the motorized stages in some existingautomated-microscope configurations are unstable. Consequently, theseexisting systems cannot rapidly, accurately, precisely and repeatedlylocate and focus on diagnostically significant areas of a sample from aspecimen.

[0013] Traditional optical microscopes, for example, enable movement ofthe stage by way of a cantilevered system that is offset from theoptical path of the microscope. In other systems, as the presentinventors have recognized, the stage is moved through the exertion of aforce at a position other than the center of gravity or center of effortof the plate. Consequently, existing microscopes tend to generate yaw,pitch, roll and droop errors (i.e., introduce a third derivative,“jerk”) during stage movement. These errors are particularly troublesomein the context of automated computer-aided microscopy. It is alsoproblematic for human observers who also need stage motion to bedampened before they can visualize a temporally stable image.

[0014] Similarly, in microscope systems that employs a detector (such asa camera) to capture magnified images, the detector itself must remainstable during operation. However, in most such systems, the detector isattached only to the viewer of the microscope. As recognized by thepresent inventors, this configuration thereby increases the likelihoodthat the camera will become unstable or misaligned during operation,potentially rendering the camera unable to capture magnified imagesproperly.

[0015] Further, to ensure proper operation, the sample being analyzed ina microscope needs to be properly illuminated and have proper spectraldensity. This is particularly the case in microscopes that employdetectors, such as cameras, to capture magnified images, as thedetectors are often configured to operate optimally with a particularlevel of light. This is also the case whenever there is spectral-basedanalysis of a sample. In these systems, if the sample is illuminatedwith insufficient or excessive light, or with improper spectralcharacteristics, the detector may need to compensate for the imperfectillumination and thereby operate less than optimally. Still further, thelevel of illumination in a microscope is important even for manualviewing through the oculars, as appropriate illumination is required toallow human perception of the magnified sample through the microscopelenses.

[0016] Additionally, a typical microscope includes a variety ofadjustable elements. These elements include, for instance, condenserlens focus, condenser lens centration, lamp filament centration,condenser aperture, and field diaphragm. To ensure proper operation ofthe microscope system, most or all of these elements need to be adjustedby an operator or an automated controller before analysis can begin. Forexample, to properly focus a diffused image at the light source, thecondenser lens focus must be properly adjusted. As another example, toachieve lamp photon emitter centration, an operator must typicallyadjust the microscope light source if the light source is not properlycentered. Unfortunately, however, adjustment of these elements can betime consuming and tedious.

[0017] In view of the deficiencies in the art, there is a need for animproved configuration of a high-precision, automated or computer-aidedmicroscope.

SUMMARY OF THE INVENTION

[0018] An exemplary embodiment of the present invention provides animproved microscope system. In one aspect, the system includes animproved method and apparatus for guiding the plate. In a second aspect,the system includes an improved method and apparatus for moving thestage. In a third aspect, the system includes an improved method andapparatus for maintaining proper illumination. In a fourth aspect, thesystem includes an improved method and apparatus for maintaining properspectral density. In a fifth aspect, the system includes an improvedmethod and apparatus for maintaining proper placement of the lightsource, for configuring a fixed optics system. In a sixth aspect, thesystem includes an improved method and apparatus for maintaining properplacement of the imaging system. In a seventh aspect, the systemincludes an improved method and apparatus for fixing the optics in themicroscope for an automated system. In an eighth aspect, the systemincludes an improved method and apparatus for increasing the stabilityof the microscope during movement.

[0019] The invention may facilitate enhanced electronic image captureand analysis and may be particularly suitable for use in the context ofcytological or histological sample analysis. However, the invention isnot limited to analysis of biomedical specimens but may more generallybe used for analysis of any type of sample.

[0020] A principal object of the present invention is to provide acomputer-aided microscope system that facilitates quick, stable andreproducible microscopic presentation of goals. Another objective of theinvention is to provide a microscope having geometric accuracy in thethree-motion axes. Still another object of the invention is to provide amicroscope that remains stable when performing high-speed moves.

[0021] A further object of the invention is to provide a microscope thatdoes not vary appreciably in terms of optical alignment. Yet a furtherobjective of the invention is to provide a microscope that hasconstantly controlled and repeatable illumination systems. Still anotherobject of the invention is to provide a microscope that may beincorporated into higher level imaging and analytical instruments. Yetanother object of the invention is to provide a microscope incombination with a detector, such as a camera or a photomultiplier tubeassembly, whereby the photodetector(s) remain(s) in proper alignmentduring their image acquisition operation.

[0022] These and other features and advantages of the present inventionwill be better understood by reading the following detailed description,with appropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Exemplary embodiments of the present invention are describedherein with reference to the drawings, in which:

[0024]FIG. 1A is a perspective view of a microscope system in anembodiment of the invention, in combination with other components suchas a display, barcode reader, and slide magazine;

[0025]FIG. 1B is a perspective view of two microscopes in anotherembodiment of the invention;

[0026]FIG. 2A is a side cutaway view of a guidance system for amicroscope assembly according to an embodiment of the invention;

[0027]FIG. 2B is a front cutaway view of the guidance system, a stageand light assembly of the microscope assembly shown in FIG. 2A;

[0028]FIG. 2C a side cutaway view of position switches in themicroscopic assembly;

[0029]FIG. 2D is a front cutaway view of a lower portion of themicroscope assembly shown in FIG. 2B;

[0030]FIG. 2E is a side cutaway view of the stage, including a z-axisplate, of the microscopic assembly shown in FIG. 2A;

[0031]FIG. 2F is a top cutaway view of the stage of the microscopicassembly shown in FIG. 2A;

[0032]FIG. 2G is a top cutaway view of the microscope assembly shown inFIG. 2A;

[0033]FIG. 2H is a front cutaway view of the microscope assembly shownin FIG. 2A;

[0034]FIG. 2I is a side cutaway view of the microscope assembly shown inFIG. 2A;

[0035] FIGS. 3A-3D are cutaway views of the focus drive and switches ofthe microscope assembly shown in FIG. 2A;

[0036]FIG. 4A is a side cutaway view of the centralized filament,mirrors and lenses of the microscope assembly shown in FIG. 2A;

[0037]FIG. 4B is a cutaway view of the light source assembly shown inFIG. 4A;

[0038]FIG. 4C is a block diagram of the light feedback system for thelight source assembly shown in FIG. 4A;

[0039]FIG. 4D is a flow chart depicting operation of the light feedbacksystem shown in FIG. 4C;

[0040]FIG. 4E is a diagram of a color temperature measurement systememployed in an embodiment of the invention;

[0041]FIG. 4F is a graph of current versus wavelength to determine thecolor temperature;

[0042]FIG. 4G is a flow chart illustrating steps for determining andmodifying the light level in a microscope system according to anembodiment of the invention, in order to facilitate operation at apredetermined spectral distribution;

[0043]FIG. 5A is a fixed condenser geometry of an imaging systemconfiguration of the microscope assembly shown in one embodiment of theinvention;

[0044]FIG. 5B is a top cutaway view of the fixed condenser geometry ofFIG. 5A;

[0045]FIG. 5C is a side cutaway view of the fixed condenser geometryFIG. 5B;

[0046]FIG. 6 is a side cutaway view of a microscope assembly and imagingsystem according to another embodiment of the invention;

[0047]FIG. 7 is a perspective view of the base and bridge of themicroscope assembly;

[0048]FIG. 8 is a side cross-sectional view of the microscope assemblyincluding the bridge, base and optical center line;

[0049]FIG. 9A is a perspective view of the Z-axis plate, guideposts,spacer post, bushings, lower plate and collar of the microscopeassembly;

[0050]FIG. 9B is a cross-sectional view of the Z-axis plate, guideposts,spacer post, bushings, lower plate, collar, base and elevation screw ofthe microscope assembly;

[0051]FIG. 9C is a top view of the collar;

[0052]FIG. 10 is a cross-sectional view of the Z-axis elevation screwdrive including the nut, elevating screw, collar, radial bearings,thrust bearing and base;

[0053]FIG. 11A is a perspective view of a microscope system in anembodiment of the invention which includes a rotating wheel; and

[0054]FIG. 11B is a top view of the rotating wheel with slots.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0055] Referring to FIGS. 1-6, there is shown a schematic block diagramof a system that incorporates the principles of the invention. Inparticular, the Figures illustrate a system having the capability tocapture images of a sample from a specimen collected from an individualand placed upon a slide, and to analyze the sample rapidly, accurately,and precisely. The microscope system may be incorporated into a varietyof settings and a variety of applications.

[0056] Exemplary Applications for Microscope System

[0057] Referring to FIG. 1A, there is shown one example of a suitableconfiguration employing a microscope system according to the presentinvention. An automated video microscope having image analysiscapabilities is coupled to a Data Management System (DMS). In oneembodiment of the invention, the DMS comprises a conventional computersystem with a processor and memory that contains patient medical historyand demographic data relevant to the specimens being screened. The DMSpreferably takes the form of a programmed general purpose desktop IBM-PCcompatible computer which has sufficient storage and processingcapability to run the Microsoft Windows operating environment and theMicrosoft Visual Basic and Microsoft Access application programs. TheDMS and the image analyzer are preferably coupled via a high-speedserial data link. The DMS may also be coupled to other data processingequipment via various types of local or wide area networks. Inalternative embodiments, other data computing equipment may be used aswould be known to persons of ordinary skill in the art. As shown in FIG.1A, a slide magazine 18, a bar code scanner 21 and display 17 may beused in combination with the microscope.

[0058] Referring to FIG. 1B, there is shown a second application of themicroscope. Automated sample analysis system 23 includes a microscopewith fixed optics, described subsequently, and a computer system.Samples are input via a slide magazine feeder 19 and analyzed with thecomputer in combination with the microscope. The data from the analysisis sent via a cable 24 to an operator-based sample analysis system 25,which also includes a microscope. The operator-based sample analysissystem 25 receives the data from the automated sample analysis system23, and, with the assistance of the data, facilitates presentation ofareas of the sample to the operator for analysis.

[0059] The microscope may be used in combination with a detector forsensing the magnified image of the sample, as discussed subsequentlywith respect to FIG. 6. In one embodiment, the detector is a highresolution, scientific grade charge coupled device (“CCD”), such as maybe used in a video camera. However, the invention is not limited to useof a CCD, but may use other means for capturing or viewing an image.Such devices may include, for instance, in addition to CCD cameras andtraditional video cameras, photomultiplier tube (PMT) assemblies. Thecamera is preferably affixed to a video-port on top of the eyepiece ofthe microscope in order to capture cell images. A variety of cameras areavailable, depending on the resolution requirements (including spectralresolution, spatial resolution, photometric resolution and temporalresolution) of the user. Three available video cameras include thePulnix TM-1001 available from Pulnix Corp. of Sunnyvale, Calif., theKodak Megaplus ES1.0 from Eastman Kodak of Rochester, N.Y. and the SMD1M15 from Silicon Mountain Devices of Colorado Springs, Colo. A lenswith 10× magnification, 4.0 numerical aperture (other magnifications ornumerical apertures may be chosen depending on the ultimateapplication), provides the combination of a large field of view as wellas the high spatial resolution to facilitate efficient specimenscreening by a single objective lens.

[0060] Images received by the camera are captured by a Data Raptor typeframe grabber available from Bit Flow Corp., Woburn, Mass., andtransferred to an image analyzer for analysis. The microscope and imageanalyzer are coupled by a serial data link which permits the imageanalyzer to initiate control of an autofocus function on the microscopeand to capture specimen position information. The microscope ispreferably controlled by a controller board, which is described infurther detail in U.S. Pat. No. 5,930,732, entitled “System forSimplifying the Implementation of Specified Functions,” the entirety ofwhich is hereby incorporated by reference.

[0061] General Arrangement

[0062] Referring to FIGS. 1 and 2A-2G, there are shown various views ofa microscope 10. In the exemplary embodiment, microscope 10 includes anumber of sub-elements, including a base 12, a Z-axis plate 13, a Y-axisslide 14, an X-axis slide 15, magnifying lens(es) (such as objective16), slide holder 19, eyepiece 20, and light source 77. The Z-axis plate13 supports the slide containing the sample and can move the sample inthe Z-direction, as shown in the Figures. As further shown in FIG. 2F,the Y-axis slide 14 moves the sample in the Y-direction via a motor 43,and the X-axis slide 15 moves the sample in the X-direction via a motor41. The slide is held in a carriage 45 which moves in the X-direction.

[0063] Base 12 provides rigid support for the microscope and, as shownin the Figures, may form the bottom portion of the microscope. In analternative embodiment, the base may include an upper portion as shownin FIG. 6, as discussed subsequently. Moreover, in FIGS. 2A-2D and FIGS.2G-2I, the light source 77 is attached to the base and the path of lightfrom the light source 77 travels through the base. In an alternateembodiment, the light source 77 may be attached to an upper portion ofthe microscope.

[0064] The controller board within the microscope 10 receives signalsfrom the multifunctional control unit. The controller board preferablygenerates and transmits signals to control the operation and movement ofthe aforesaid components of the microscope, and to transmit and receiveinformation generated by sensors on the microscope, via ports 66 asshown in FIG. 2A, to and from the DMS. In some embodiments, thecontroller board may control the transmission and selection ofinformation between the microscope 10, camera, frame grabber, imageanalyzer, and the DMS. In still other embodiments, the controller boardmay be used to control the operation and movement of the components ofthe microscope 10. The images received from the microscope 10 may alsobe selectively sent to a computer for processing. The controller boardalso controls the light level, the power turret, which selects the lensfor viewing the sample, the stage translation speed, the spatialorientation of the sample on the Z-axis plate 13, the Y-axis slide 14and the X-axis slide 15, and the intensity and colortemperature/illumination control.

[0065] Referring to FIG. 2C, there is shown a side cutaway view of thelower portion of the microscope including position switches 58. Includedin this portion is the stage 27, which is shown as side and top cutawayviews in FIGS. 2E and 2F, respectively. The stage 27 typically is theportion of the microscope that provides movement of the sample. Thestage 27 may move upward and downward during focusing and may include aplate, such as a Z-axis plate 13. A plate may be an object that, eitherdirectly (by direct physical contact) or indirectly (through anotherobject), holds the sample. In a preferred embodiment, the stage 27includes the Z-axis plate 13, the Y-axis slide 14, the X-axis slide 15,the condenser lens system 29, and guideposts 55. As discussedsubsequently, the Z-axis elevation system employs an elevating screwwhich is in contact with the lower portion of the Z-axis plate 13.Moreover, movement in the x-direction and y-direction is performed bymotor 41 and motor 43, respectively.

[0066] Vertical Movement and Guidance of Microscope Stage

[0067] Because of the design of the present invention, the microscope 10is very precise and accurate. The improved microscope 10, for instance,enables a cytotechnologist or other observer to rapidly, precisely andaccurately locate objects of interest with the requisite positionalaccuracy and precision, e.g., in cytological applications, within ±5microns. In addition, the microscope of the present invention may bemanufactured at a moderate price while still maintaining high precision.In particular, the invention permits development of a system of precisetolerance components which, when assembled with a thermoset plasticmaterial, yields the required performance accuracy. In addition, thesystem has proven to be dimensionally stable. In order to achieve alevel of accuracy and stability similar to the present invention, aconventional microscope would require extremely precise components,rendering the cost of the microscope financially impractical.

[0068] The stage 27 is moved along the Z axis by a device that appliesforce at a specific point on an underside of the Z-axis plate 13. Asdiscussed subsequently, the Z-axis elevation system employs an elevatingscrew 89 which is in contact with the lower portion of the Z-axis plate13. The force is preferably applied at a single point via the elevatingscrew 89, which, in a preferred embodiment, works in combination with amotor assembly. The elevating screw 89 is, in one embodiment, 8 mm indiameter with a 0.5 mm pitch. This placement of a single, specific pointof force on the Z-axis plate 13 of the stage provides for greaterstability when moving the stage 27. If a single point of force formoving the stage 27 is chosen, it is preferably applied at, orsubstantially at, the center of gravity of the stage 27 in order toreduce the amount of geometric errors. This configuration improves overtypical microscopes, in which the manner of moving the stage is to applyforce to the plate at points that are not at the center of effort orgravity. For example, a typical cantilever bearing system (commonlyreferred to as the knee and column design) may increase the possibilityof geometric errors while viewing due to the offset manner of moving thestage. Moreover, as the inventors have discovered, this prior art methodcreates instability while moving the stage.

[0069] According to the current method and apparatus, the force formoving the stage upward and downward is concentrated at the center ofgravity 139 of the stage (which includes the X-axis slide 15, Y-axisslide 14 and Z-axis plate 13), as shown in FIG. 2G. In this manner, thepoint of force for moving the stage is preferably limited to a singlepoint, typically the center of effort. In an alternative embodiment,there may be a multitude of forces applied at various points on theplate to move the Z-axis plate 13 (and in turn the stage 27) upward anddownward. The net effect of these forces is that there is an upward ordownward force at, or substantially at, the center of gravity of thestage. For example, a multitude of forces may be applied at differentpoints on the stage, with the net force being at the center of gravityof the stage and in the Z direction or in the direction of the opticalpath. In addition, the application of force at this point inherentlymaintains stability of the system during movement. The device, or“forcer,” that is used to apply force to one point may take a variety offorms. As examples, the forcer make take the form of a piston, leadscrew, finger, lever, column, cam, gear system using rack and pinion, orpiezoelectric device or voice coil. Referring to FIGS. 2H and 2I, thereare shown front and side cutaway views of the microscope assembly.

[0070] In the exemplary embodiment, the arrangement for verticallymoving stage 27 advantageously takes the form of a single jack screwsitting in a radial/axial thrust bearing system. Referring to FIGS. 3Aand 3B, this arrangement is shown in more detail as apparatus 56 locatedbeneath the Z-axis plate 13. The assembly of this apparatus containsradial ball bearings 57 and nut 87 fixed within the bearings 57.Specifically, ball bearings 57 have an inner race in contact with nut 87and an outer race in contact with base 12 (so that the outer race doesnot move). An elevating screw 89, which is in contact with the Z-axisplate, engages nut 87.

[0071] The Z-axis plate 13 is gravity-loaded against a thrust bearingfor the elimination of focusing hysteresis (backlash) while moving theZ-axis plate 13. In an alternative embodiment, the elevating screw, orother means for applying force at one point to the Z-axis plate 13, maybe attached to the Z-axis plate 13. A synchronous timing belt and pulleysystem 61 coupled to a motor 59. As shown in FIG. 3A, the motor 59 isadjacent to the ball bearings 57 and nut 87. Thus, when the Z-axis plateis to be moved vertically, the motor assembly 59 moves the pulley 61,which then turns the nut 87 and the inner race of bearings 57. The nut87 in turn moves the elevating screw 89. Via a coupling 103, theelevating screw 89 moves the Z-axis plate 13. In the exemplaryembodiment, the elevating screw is an 8 mm diameter hardened ball screwwith a pitch/lead of 0.5 mm, and the net result of the gear reduction isthat one microstep (or one step of the motor) equals {fraction (1/16)}micron elevation of the stage.

[0072] The screw may be made of a heat treatable steel such as Timkenball bearing steel (AISI-52 100). Preferably, the elevation screw, thenut and the balls are all made of the same material, treated to a highlevel of hardness, such as Rc-62/64. In that way, it is believed therewill be no possibility of brinelling (i.e., the disruption of smoothsurfaces from interplay between components), which could otherwiseinterrupt the smooth rolling of balls 57 and give rise to abrupt motion.

[0073] As thus shown and described, in the exemplary embodiment, thearrangement of components that move the stage vertically, i.e., theelevating screw 89, the nut 87, and the bearings 57 (as well as aportion of pulley assembly 61), forms a single-column assembly. Asfurther shown in FIG. 3A, this single-column assembly is rigidly mountedto base 12 by bosses 35, which is a raised surface that is part of thebase 12, machined to accept the single column assembly.

[0074] Further, this single-column arrangement is itself inherently veryrigid compared to the typical microscope focus systems, which usuallyemploy gear box designs. In traditional arrangements, a focus system maygo through a 12-14 gear reducer system, which normally has largehysteresis, play, lash and spring. With such systems, manufacturerstypically cannot guarantee less than 5 micron hysteresis. With thepresent jack screw arrangement, in contrast, dramatically fewer partsare required. In effect, the screw 89 itself can be static (except forup and down movement), and the only moving part might be nut 87, whichrotates in the radial axial bearing arrangement. Advantageously, thisarrangement should be able to provide closer to {fraction (1/16)} micronor better hysteresis, a significant improvement over the existing art.

[0075] Turning back to FIG. 2G, there is shown the motor assembly 137that applies a point of force on the Z-axis plate 13 at the center ofgravity 139 of the Z-axis plate 13. In an alternate embodiment, as shownin FIG. 3B, the motor assembly may be offset from the center of gravityof the Z-axis plate 13.

[0076] The stage 27 theoretically does not require anything foroperation in addition to the elevating screw 89 and the associated motorassembly. This is due to the fact that the elevating screw 89 moves thestage 27 at its center of gravity. However, on a practical level, thestage 27 may experience movement in the X and Y directions duringoperation. For example, the elevating screw 89 is designed to providethrust in the Z-direction. In addition to the thrust, there may alsoinclude lateral movement in the X- and/or Y-direction. In order toreduce or minimize this movement, a guidance system is used. Theguidance system assists in maintaining proper alignment of the stage 27with respect to the optical axis. The guidance system of the microscopeof the present invention is preferably centered or substantiallycentered around the optical path through the Z-axis plate 13 of themicroscope. An optical path is defined as the path through which lightpasses through the microscope. One portion of the optical path isthrough the stage 27 of the microscope. Of primary importance are thestability and geometric accuracy of the system at the optical path.According to a preferred embodiment, this stability may be achieved bycentering the guideposts around the optical path. This is in contrast toguidance systems of typical microscopes, which are not centered aroundthe optical path of the microscope and which may have an overhang ofcomponents. These existing systems are typically unstable and arethereby prone to producing yaw, pitch and droop errors of the stage (andtherefore the image) due to a lack of stability in design.

[0077] In an exemplary embodiment, the method for guiding the Z-axisplate 13 is via a plurality of guideposts 55, as shown in FIGS. 3A-C.Each of the guideposts 55 is preferably equidistant from andapproximately symmetrically placed around the optical path through theZ-axis plate 13. As shown in FIG. 2G, the center of the locus of pointsof the guidance system for the Z-axis plate 13 and stage 27 iscoincident with the optical path. For example, the guidance system maybe clustered in an array, with the array being any number greater thanone. The center of that array should be coincident with the opticalpath. So that, if one takes a cross-section of the guidance systemperpendicular to the optical path, that center of the array is at orsubstantially at the optical path.

[0078] The guidance system in one embodiment includes two portions, oneportion being a part of or attached (either removably or permanently) tothe stage or the plate (such as the Z-axis plate) and the other portionbeing a part of or attached (either removably or permanently) to thebase. For example, in one embodiment, the guideposts 55, which areattached to the Z-axis plate 13, are the first portion and ball bushings54, which are attached to the base 12, are the second portion. Theguideposts 55 and the ball bushings 54 mate with each other to stabilizemovement, and are discussed subsequently with respect to FIGS. 3A-D. Theguidance system in another embodiment includes two portions, one portionbeing an integral part of the stage or plate and the other portion beingan integral part of the base. For example, the Z-axis plate may haveholes which engage guideposts that are integral with the base or areaffixed to the base. In an alternative embodiment, a plurality ofguideposts at varying distances from the optical path are used. Inparticular, a first set of guideposts is a first predetermined distancefrom the optical path (with each guidepost being at the same firstpredetermined distance from the optical path) and first angulardisposition (the guideposts being distributed around the circumferenceof the optical path), whereas another set of guideposts is at a secondpredetermined distance from the optical path (with each guidepost beingat the same second predetermined distance from the optical path) andsecond angular disposition (the guideposts being distributed around thecircumference of the optical path).

[0079] Referring to FIGS. 2E and 3A-D, there are shown cutaway views ofthe focus drive and switches of the microscope assembly. Three boreholes 51, 52 and 53, discussed subsequently, are placed in the Z-axisplate as shown in FIG. 2G. Moreover, recirculating ball bushings 54, asshown in FIG. 3A, are attached to the base 12 and are preloaded into thebore holes 51, 52, 53 of the Z-axis plate. The recirculating ballbushings 54 act as guidepost mates that engage the guideposts 55.Guideposts 55, preferably machined to a tolerance of millionths of aninch, are affixed to the bore holes 51, 52, 53 and run in the bushings54. The bushings 54 and the guideposts 55 are designed such that theyoperate with essentially zero clearance. In particular, the bushings 54contain bearings that are rolling balls operating in an interferencemode with the guideposts 55, so that there is no off-axis motion. Thus,the movement of the stage 27 is vertical with no lateral play. Due tothis design, the stage 27 may operate with vertical movement typicallyin {fraction (1/16)} micron increments. Other types of guidance systems,such as a linear bearing system, flexure plates, air or magneticbearings or a dovetail slide with gibs system, are possible as well.Moreover, as shown in FIG. 3C, one of the guideposts 55 is extended inlength so that at a certain level, the guidepost engages switches 58.The switches 58 thereby may indicate the position of the Z-axis plate13.

[0080] Referring to FIGS. 2A-C, there is shown side, back and topcutaway views of the microscope assembly, respectively. The opticalmicroscope 10 includes a stress annealed aluminum Z-axis plate, havingprecision bored holes 51, 52, 53. These holes are preferably bored witha key tolerance of about 10 microns. The number of bored holes may varydepending on the mechanics of the microscope assembly. The heat treatingof the cast aluminum member increases dimensional stability. Inaddition, the precision bored holes allow the Z-axis plate 13 to movealong the optical path in a smooth manner, i.e., without jittery,shaking or jerky motions, during scanning and focussing. The Z-axisplate 13 is preferably cast aluminum, which may be rough machined. Then,the Z-axis plate 13 may undergo heat treatment for stress relief.Thereafter, the holes may be precisely bored into the Z-axis plate 13 soas to be aligned accurately and non-changeably with time. Therefore, dueto the centration of the guidance system around the center of gravity,errors of droop, pitch and yaw tend to nullify or to cancel themselvesto zero.

[0081] Light Source Alignment and Emission

[0082] Referring to FIG. 4A, there is shown a side cutaway view of thecentralized filament, mirrors and lenses of the microscope assembly.Condenser lenses 63, 65 receive light through a numeric aperturediaphragm 67, which in turn receives light through a mirror system 69,through a field diaphragm 71, a filter diffuser 73, a second mirrorsystem 75, a second filter diffuser 76. Light is generated by a halogenlight source or any other light source with a centralized photon emitter(i.e., illumination source). Means have been developed for a photonemission module to be easily replaced without the necessity ofcomplicated or costly efforts at realignment of parts or processes, asdiscussed subsequently.

[0083] In addition, light may be generated from any light source whosephoton emitter (e.g., filament) is at a predetermined location from thebase, screw or other mounting geometry of the light source. Once thebase or other mounting geometry is properly aligned, the photon emitteris likewise aligned with the optical path due to the predeterminednature of the light source. The optical alignment is therefore obtainedby machining components rather than by adjusting the light source,thereby minimizing error. In the case of a centralized photon emitter,the photon emitter is centered with the base or other mounting geometryof the light source.

[0084] Such an automated system requires precisely defined illumination.Such defined illumination is required when the system is initially used,throughout the life of use of the lamp (which may decrease in itsillumination over time), and throughout the life of any replacementlamps. The present invention thus maintains consistent and preciseillumination throughout use of the microscope. In conventional systems,when a light source is initially installed or replaced, the system mustbe realigned by a technician in order to minimize uneven illuminationwhich may be received by the camera. In an embodiment of the currentinvention, the design of the system and the light source are such thatthe system is pre-centered due to the predetermined spatial relationshipof the photon emitter with the mounting geometry of the light source anddue to the mounting mechanism for the light source on the microscope.Thus, when a light source burns out, replacement of the light sourceautomatically centers the photon emitter, as described below (within 2thousandths of an inch of the theoretical center line).

[0085] Referring to FIG. 4B, there is shown a cutaway view of the lightsource assembly. The light system is unlike a conventional microscopelight source configuration, at least in part, since it has a photonemitter that is at a predetermined spatial location relative to areference feature of its housing (e.g., the base 92 or the mountingmechanism for the light source) and due to the mounting mechanism of themicroscope. In a preferred embodiment, the light source 77 is a halogenlight source with a photon emitter 94 that is at a predetermined spatiallocation with the base 92, due to precise and accurate manufacturing ofthe light source. The distance from the base to the photon emitter is 20millimeters in the Welsh Allen, part no. 1036-1. Since the light source77 is designed to have a photon emitter 94 at a predetermined axial andradial distance from the base 92 of the light source, the base 92 may becorrectly positioned thereby correctly positioning the photon emitter.In this manner, the design of the illumination system enables lamps tobe installed with near perfect centration.

[0086] In the present invention, any light source may be used, dependingon the power requirements, so long as the photon emitter, or the meansfor generating the light, is at a predetermined axial distance from thebase of the light source (i.e., the predetermined distance from onelight source to the next is the same within an acceptable tolerance). Ina preferred embodiment, a halogen light source is used. In addition, alight source in combination with a fiber optic cable, an incandescentlight source, a light emitting diode (LED), an arc lamp (e.g., xenon arclamp or mercury arc lamp), or other such light source (with or withoutwavelength selection means) may be used.

[0087] The optical path 96 of the system is designed to be directed fromthe center of the halogen light source with a centralized photon emitteror filament. Therefore, the halogen light source with a centralizedphoton emitter sends light directly (and with minimal shadowing) ontothe physical image on the slide. In particular, in a preferredembodiment, the lamps are manufactured by Welsh Allen, part no. 1036-1,30 watt halogen light sources with a centralized photon emitter. Thehousing 79 that receives the lamp is also designed such that the halogenlight source with a centralized photon emitter 77 may be placed withmaximum accuracy and placement reproducibility. In this manner, when thebase of the light source is positioned properly, the photon emitter ofthe light source is positioned properly as well.

[0088] The housing 79 contains a mounting mechanism for receiving thelight source. The mounting mechanism is designed to receive the lightsource 77 precisely, both concentrically and axially. The mountingmechanism, in one embodiment is an accurate and precise boring of a hole91 in the housing 79. Other mounting mechanisms, such as clamps, may beemployed wherein the mounting mechanisms concentrically and axiallyplace the light source in housing 79.

[0089] In addition, the hole 91 is of sufficient axial and radialpositional accuracy to provide the imaging system with a positionaltolerance of about 0.127 millimeters. This precision boring receives thebase 92 of the light source. In addition, a seat 95 is precisely boredand/or shaved so that the base 92 of the light source abuts the hole 91in perfect alignment. The precision boring of the hole 91 and the seat95 thereby ensures that the base of the light source 77 is in its properplacement. In addition, a threaded hole 98 is bored to engage the screwmount 100. The screw mount 100 attaches the light source 77 within thehousing 79 and makes electrical contact with the compliant contact 102in the housing 79. Because the photon emitter is at a predeterminedlocation relative to the base, the photon emitter of the light source 77is in proper alignment and centered at the optical center line. Power isconnected to the light source 77 via wires 97 and a connector 99.

[0090] In addition to proper placement of the light source, theintensity of the light source can be controlled. In both an operatordriven system (in which, for example, the operator views the magnifiedimage through an eyepiece in the viewer) and a detector based system (inwhich, for example, a detector, such as a camera, receives the magnifiedimage from the viewer and acts as an electronic image viewer), theproper amount of light can be generated to illuminate the sample. Inparticular, in a detector based system, the detector may have an optimallight level (or optimal light range) under which it operates. Forexample, when using a camera, the camera has a range of optimal valuesof light for operation. When the camera receives an image with less thanthe optimal value of light, it adjusts the shutter speed to lengthen theexposure time. Similarly, when the camera receives an image with morethan the optimal value of light, it adjusts the shutter speed to shortenthe exposure time. To better capture the image from the detector, thelight level should therefore be chosen so that the detector operates inits optimal light range.

[0091] In order to accomplish this, a detector is used to sense lightthat is in the optical path 96. The light travels from light source 77and is ultimately sent to the viewer. As shown in FIG. 4A, the lighttravels from the light source 77 to the second filter diffuser 76 to thesecond mirror system 75 to the filter diffuser 73 to the field diaphragm71 to the mirror system 69 to the numeric aperture diaphragm 67 to thecondenser lenses 63, 65. In order to determine the intensity level ofthe light, the light may be sensed at any point in the path of the lightsource through the microscope. In FIG. 4a, the mirror system 69 is a98/2 mirror that reflects 98% of the incoming light and passes 2% of thelight. Behind the mirror system 69, a detector in the form of lightintensity monitor system 101 senses light that passes through the mirrorsystem 69. The light intensity monitor system 101 is an electroniccomponent such as a diode that feeds back information to the computersystem or processor, which controls the light level of the lamp, asdescribed subsequently. In addition, any form of light detector may beused to sense the light.

[0092] There are methods in which to both sense and control theintensity of the light. Referring to FIG. 4C, there is shown a blockdiagram of one preferred embodiment of the light feedback system. Thelight source 77 generates the light and has a power sub-block 111. Inone possible embodiment, the power sub-block 111 includes wires 97 andconnector 99, which connects to one end of the light source 77. Thelight is sensed by a detector 105. The detector 101 sends its output toa processor 105, which contains a comparator 107 and a look-up table109. The look-up table 109 may take the form of a permanent memory suchas read only memory (ROM) or a temporary memory such as random accessmemory (RAM). Depending on the operation of the processor 105, describedsubsequently with respect to FIG. 4C, the processor alters the amount ofpower to the light source in order to adjust the level of illumination.

[0093] Referring to FIG. 4D, there is shown a flow chart for determiningand modifying the light level in the microscope system to operate at aprecise amount of illumination. A portion of the light that is generatedfrom the light source is sensed via a detector, as shown at block 113.This value is sent to the processor 105, which determines whether theamount of light generated is within the optimal range. In particular,the processor determines whether the light is greater than the upperbound of the optimal range, as shown at block 115, or whether the lightis less than the lower bound of the optimal range, as shown at block121. In the preferred embodiment, as shown in FIG. 4A, because of the98/2 mirror 70, the detector 101 senses 2% of the light. Therefore, theprocessor 105 is able to determine, based on the sensed light, how muchlight is being generated. In addition, the light may be sensed at anypoint in the optical path, from near the photon emitter 94 of the lightsource 77 to the condenser lenses 63, 65.

[0094] Look-up tables 109 in the processor 105 have a firstpredetermined value and a second predetermined value. These valuesdefine the amount of sensed light from the detector when the lightsource is operating in the upper limit of the optimal range and thelower limit of the optimal range, respectively. In addition, thesepredetermined values may be generated during calibration of themicroscope. The first predetermined value indicates that the amount oflight in the microscope is at the upper limit of the optimal range andthe second predetermined value indicates that the amount of light in themicroscope is at the lower limit of the optimal range. Using thecomparator 107, the sensed light is compared with the firstpredetermined value to determine if the sensed light is greater thanthat value, as shown at block 115. If it is, then too much light isbeing generated by the light source and the amount of power to the lightsource should be reduced. The sensed light is also compared to thesecond predetermined value to determine if the sensed light is less thanthat value, as shown at block 121. If it is less, then too little lightis being generated by the light source and the amount of power to thelight source should be increased.

[0095] To regulate the amount of power to the light source, theprocessor first determines the amount of power that is currently beinggiven to the light source, as shown at block 117. In one embodiment,this is done by sensing the amount of current sent to the light source.In another embodiment, the processor has the value of the amount ofpower that corresponds to the amount light detected stored in thelook-up table. If the sensed light is greater than the firstpredetermined value, the amount of power to the light source is reduced,as shown at block 119, corresponding to the amount of the sensed lightthat is greater than the first predetermined value. On the other hand,if the sensed light is less than the second predetermined value, theamount of power to the light source is increased, as shown at block 125,corresponding to the amount of the sensed light which is less than thesecond predetermined value. In an alternate embodiment, the light levelis adjusted, either upward or downward, by incrementing the current tothe light source upward or downward. This determination of the lightlevel in the optical path is preferably continuous when the machine isin use.

[0096] In addition to controlling the intensity of the light source, thespectral distribution of the light source should be controlled in orderto obtain the proper color-fidelity image. Imaging systems, such asphotographic film or cameras, have a certain spectral distribution inwhich they best operate. In order to obtain the best image from theimaging system, one must choose the illumination from the light sourcein order to be within the optimal spectral distribution of the imagingsystem. In addition, analysis of specimens may be spectrally based. Inthose instances, the correct spectral distribution removes potentialerror based on varying illumination.

[0097] One measure of the spectral distribution is the colortemperature. The color temperature is a measure of the intensity of thelight at different wavelengths. Therefore, analysis of the colortemperature indicates the spectral distribution of the light in themicroscope. In an alternative embodiment, the spectral distribution maybe sensed at a band of wavelengths or across the entire electromagneticspectrum.

[0098] Typically, an incandescent light source shifts its spectraldistribution of the light (and hence its color temperature) when thelight source increases or decreases illumination. At the lowestillumination levels, the majority of the incandescent light may be inthe infrared light range. As the illumination increases, the peak of thewavelength shifts to the visible light range eventually shifting to theultraviolet light range.

[0099] In order to maintain proper illumination during operation of themicroscope, the proper illumination is determined during initialcalibration of the microscope. Also, during calibration, measurementsare taken at wavelengths to determine the proper intensity at thewavelengths for the proper illumination. Thereafter, during operation,the intensity is tested at the wavelength(s) to determine whether theintensity of the light source should be increased or decreased.

[0100] Referring to FIG. 4E, there is shown a diagram of a spectrumdistribution measurement system that measures color temperature. Theincoming light is sent to a dichroic beam splitter 141, which splits thelight into two parts with high efficiency. Other forms of beam splittersmay be used depending on the efficiency necessary. The split beams arethen sent to wavelength selection filters 143, 145 whereby a narrow bandof wavelengths are passed. Thereafter, the filtered light is sent toDetector λ₁ 147 and Detector λ₂ 149 which generates a current (orvoltage depending on the sensing circuit) as a function in thecorresponding wavelength. Detector λ₁ 147 and Detector λ₂ 149 in oneembodiment are both photodetectors (e.g., diodes). In anotherembodiment, the selection filters and diodes may be integrated into onepackage. Further, in a preferred embodiment, the selection filters anddetectors are placed closer, and sense light closer, to the light source77. In an alternate embodiment, selection filters and detectors areplaced closer to the condenser lenses 63, 65 in order to sense anychanges in the spectral distribution as light travels through themicroscope system.

[0101] A graph of a spectral distribution of current (I) versuswavelength (λ) for two different illuminations is shown in FIG. 4F.Referring to FIG. 4G, there is shown a flow chart for determining andmodifying the light level in the microscope system to operate at apredetermined spectral distribution. The color temperature isproportional to I_(λ1)/I_(λ2). Therefore, in order to determine thechange in color temperature (and hence spectral distribution), thepresent measurement of the proportion is compared to the proportionmeasured during calibration of the system (when the system was operatingwith an optimal spectral distribution). The amount of light is sensed atcertain wavelengths, λ₁ and λ₂, as shown in block 151. Depending on theamount of light sensed, currents are generated in the detectors, asshown in block 153. Depending on the comparison between the outputs ofDetectors λ₁ and λ₂, and a value which is determined during calibration,the current or voltage of the light source is modified, in order tomaintain a constant color temperature (and hence constant spectraldistribution). For example, if λ₁ is greater λ₂, and the currentproportion of I_(λ1)/I_(λ2) is less than the calibrated proportion(which is stored in the same look-up table, or similar look-up table asthe table 109 in FIG. 4C), as shown in block 157, the spectraldistribution is too far into the infrared range, so the illuminationshould be increased (by increasing the voltage or current), as shown inblock 159. Likewise, if the current proportion of I_(λ1)/I_(λ2) isgreater than the calibrated proportion, as shown in block 161, thespectral distribution is too far into the visible region or ultravioletrange, so the illumination should be decreased (by decreasing thevoltage or current), as shown in block 163. In this manner, constantcolor temperature may be maintained in order to optimize the use of theimaging system and maintain the integrity of spectral-based analysis.

[0102] As discussed previously with respect to FIGS. 4A-4D, theintensity of the light source may be controlled by varying the current(or voltage) to the light source. The greater the intensity desired, thehigher the current (or voltage). However, when attempting to integratecontrol of both intensity and spectral distribution (or colortemperature), means other than modifying the intensity at the lightsource are used to control the intensity. For example, one may separatethe two functions by controlling the color temperature through theadjustment of the lamp power and by controlling the intensity by usingcrossed polarizers in the optical path. Depending on the intensityrequired, the polarizers may be turned to modify the intensity of thelight. If polarized light is not conducive to the imaging system, apolarizer scrambler may be used in combination with the polarizers.Other means may be used to shield a portion, or all, of the light in theoptical path without altering the power to the light source. Anothermethod to modify the intensity without influencing the color temperatureis through neutral density filters. Moreover, any means known to thoseskilled in the art that does not influence the spectral distribution orcolor temperature but affects the intensity may be used.

[0103] In an alternate embodiment, a selection filter placed in front ofthe detector 101 for the intensity illumination in FIG. 4A may sensedata both for color temperature and for intensity. The single detectormay sense the intensity at one wavelength. Assuming a constant spectraldistribution for a variety of intensities, both the intensity and thecolor temperature may be determined. Moreover, in an alternateembodiment, a wavelength selection means 72 which selectively passes asingle wavelength or a band of wavelengths may be placed anywhere theoptical path.

[0104] Referring to FIG. 5A, in one embodiment of the invention that isof particular utility in an automated system, there is shown a fixedcondenser geometry of an imaging system configuration of the microscopicassembly, as used in the automated sample analysis system 23 in FIG. 1B.In systems which are completely automated, the optics are designed withfixed rigid optics that are prealigned. During initial calibration ofthe microscope, the placement of certain optics, including the condenserlens(es) and the numerical aperture, are Therefore, once assembled,aspects such as the focus, the diaphragm size, the aperture, etc. arefixed. FIG. 5A is shown with the lenses all fixed in locations by acondenser lens body 80. Once built, the lenses cannot change inposition.

[0105] In order to design a system that may be configured as a fixedoptic system, a portion of the optical system, as shown in FIG. 4A maybe designed with the fixed optics, as shown in FIG. 5A. The opticalsystem is reconfigured with lens focusing and pupil apertures allestablished by machined and locked settings during initial calibrationof the microscope. This insures that the system is always in thecalibration established at the time of setup. Referring to FIG. 5A, thecondenser lenses 63, 65 in one embodiment may be fixed rigidly to themicroscope. Also shown is the objective 16, which is one type ofmagnification lens. Condenser lens 63 and condenser lens 65 are placedwithin a housing 68, as shown in FIG. 5C, a predetermined distance apartusing spacers 81 to maintain the separation. In addition, numericalaperture 67 has a fixed pupil and is held rigidly by abutting thenumerical aperture 67 against a ledge 86 and placing a snap ring 83 tohold the numerical aperture 67 (with a fixed aperture) rigidly in place.The ledge 86 may be machined in order to properly align the numericalaperture 67 during calibration of the microscope. Another ledge 85 maybe machined in order to affix the assembly with the condenser lenses 63,65 and numerical aperture 67. Mounting screws 88 are used to adjust thefit, which is thereafter permanently affixed by pins 90, as shown inFIG. 5A and 5B, so that condenser lens body 80 is attached to the Z-axisplate 13. In this manner, the condenser lenses 63, 65 and the numericalaperture 67 are permanently in focus and do not require adjustment.Further, the field diaphragm 71 is fixed to the base, as shown in FIG.2G, and has a fixed pupil. In an alternative embodiment, for a lightsource that is not attached to the base, the field diaphragm may beattached to a portion of the microscope other than the base. However,the field diaphragm still has a fixed pupil.

[0106] Imaging System

[0107] Referring to FIG. 6, there is shown a side view of a microscopewith an attached imaging system. In one embodiment, the imaging systemis a camera 127. The imaging system is affixed to the microscope,according to one embodiment, at two separate places. The first place isat the viewer portion of the microscope. The camera mounts to anextender portion 129. The extender portion 129, in one embodiment, isL-shaped with one end being connected to the camera via a screw threadC-mount 131 and the other end being connected to the microscope via adovetail portion 133. In addition, the camera 127 is attached to thebody of the microscope at a second place along the upper microscopehousing 138 of the camera itself. Referring to FIG. 6, there is shown asecond connector, which, in one embodiment is a dovetail portion 135that is connected to one side of the camera 127. The second connector isalso connected to an intermediary piece 137, such as a shim. Theintermediary piece is connected to the body of the microscope. In thisarrangement, the camera is first aligned via the extender portion 129and thereafter the camera body is rigidly fixed to mounting surfacesprovided on the microscopy frame. The camera is therefore rigidly fixedto the microscope so that during operation, the camera will not be movedout of alignment. The camera may be rigidly fixed to the microscope inmore than two places.

[0108] Connection to External Systems

[0109] Moreover, according to a preferred embodiment, the microscopysystem is designed to be integrated into a larger system containingadditional components. The microscopy system includes mounting geometryand electrical connections sufficient to allow incorporation into otherinstruments. The imaging system may therefore be designed to minimizeproblems with interconnections to other devices such as computers andthe like. The imaging system includes a connector 62, as shown in FIGS.2A and 2C. The system is designed with a centralized circuit board 64which, in turn, is connected to the connector 62. The connector 62provides data transmission to such components as the DMS discussed aboveas well as electrical connections. The system may also have fixtureswith mounting surfaces for the placement of accessories (such as a laserbar code reader). The added structure provided by these fixturesenhances the stability and thus the accuracy of the system. As shown inFIGS. 2A and 2C, there are ports 66 that provide a connection for all ofthe on-board systems for the microscope. The ports 66 allow for theconnection to other units that may work in combination with themicroscope. For example, other devices, such as a dotter, bar-codereader, power lens turret controller, slide sensor and cameracontroller, etc. may be in communication with the microscope and imagingsystem via the ports 66, for instance.

[0110] Bridge Frame

[0111] The microscope assembly described above advantageously providesfor increased stability and precision. In the arrangements describedabove, however, the microscope frame structure is illustrated as a “C”frame or cantilevered design, which is primarily dictated by a need toprovide operator access to the specimen from the front of themicroscope, effectively through the open side of the “C” structure.Unfortunately, when a microscope is used for quantitative imagingoperations, it has now been determined that the instability of thecantilevered design begins to limit the efficacy of the system. Movementcaused either within the system (such as vibrations caused by a motorwithin the microscope) or outside the system (building shaking orheating/air conditioning system) effect the operation of a typicalcantilevered system. In particular, this type of structure does not havea good dynamic stiffness. Dynamic stiffness is a measure of the dynamicresponse of the microscope (i.e., a measure of how the microscope reactsto live loads such as how much the microscope shakes, vibrates ordeflects). Microscopes which magnify an image to a great degree shouldhave a sufficiently good dynamic stiffness, particularly at the opticalcenter line. Otherwise, the microscope will shake or move to such anextent that the microscope will not be able to capture a clear image.However, the current “C” structure allows for too much variations,especially at the optical center line, limiting the ability of theimaging system to realize the maximum resolving power of the sensingelements.

[0112] According to an additional aspect of the invention, microscopestability can be further enhanced by including structure which increasesthe dynamic stiffness of the microscope with a focus on the dynamicstiffness at the optical center line. One example of the structure isshown in FIGS. 7 and 8. Referring to FIGS. 7 and 8, a brace 200 isrigidly connected between the upper portion 210 of the microscopeassembly and lower portion 212 of the microscope assembly, therebymaking the overall microscope frame structure a closed ring (from a sideview). The brace 200 is designed to work in conjunction with the upperportion 210 of the microscope assembly to make the microscope morestable during operation. In turn, rather than mounting optical elements(such as a camera, for instance) on top of a cantilevered structure, theoptical members are instead preferably mounted at the center on what iseffectively a “bridge” structure, supported on one end 214 by the braceand on another end 216 by the “back” side of the microscope frame. Inthe exemplary embodiment, these supporting structures on both sides ofthe optical element carrier (i.e., the bridge) have substantially thesame tensile and compressive characteristics as each other, therebyenhancing stability.

[0113] The structure of brace 200 is designed to afford the requisitestability. The brace 200 should be close to the optical center line,without interfering with the movement of the stage in either thez-direction or y-direction. To accomplish this, the brace 200 iscomposed of two portions, lower portion 218 and upper portion 220. Lowerportion 218 meets upper portion 220 at surface 222. The innermostportion of surface 222 is point 224 which is adjacent to the stage, butnot touching the stage, when the stage is in its outermost position(i.e., the stage is in its uppermost z-position and in its greatesty-position).

[0114] Moreover, the cross-sectional area of the brace 200 is designedto afford the requisite stability. This is due to the fact that thecorresponding microscope structure without the brace was exhibitingmovement only in the z-direction. To provide additional stability in thez-direction, the brace has a rectangular cross-section, as shown inFIGS. 7 and 8. Alternatively, if the microscope exhibits movement in thez-direction and x- or y-directions, the cross-section of the brace iscorrespondingly modified in order to provide stability in eachdirection. For example, if there is vertical (z-direction) and lateral(x- and/or y-direction) movement, the cross-section of the brace may becomposed of a “T” shape with the top portion of the “T” providingstability in the lateral direction. Alternatively, the cross-section ofthe brace 200 may be a hollowed section.

[0115] In order to empirically determine the shape of the cross-sectionof brace 200, measurements are first taken of the deflection of themicroscope without brace 200. Varying weights (e.g., 1 lb, 5 lb, 10 lb,etc.) are placed on the upper portion 210 of the microscope (without theturret and eyepiece portion) at the optical center line. In a preferredembodiment, the amount of deflection of the upper portion 210 of themicroscope is measured point 226, as shown in FIG. 8. However, theamount of deflection can be measured at any point along the opticalcenter line. Based upon these measurements, calculations are made todetermine the thickness of the brace.

[0116] This arrangement affords a maximum stiffness consistent with themass and modulus of the supporting material. In fact, this overallbridge frame arrangement is believed to increase stability by over oneorder of magnitude (compared to the microscope frame without brace 200).For example, in one measurement, the amount of deflection was 20 μmwithout brace 200 and with a representative weight, while the amount ofdeflection with brace was less than 1 μm. Further, while brace 200 maysomewhat block front access to the stage of the microscope system and toa specimen residing on the stage, such access is of decreased importancein automated imaging and screening systems, since it is rarely necessaryfor an operator to manually move the specimen on the stage.Nevertheless, in an alternative arrangement, the arrangement of FIG. 7could be varied to provide a plurality of braces from upper portion 210to lower portion 212, or to provide a single brace with a front openingfor operator access. In still an alternate embodiment, the supportingstructure may be composed of an upper section of a sphere, with a holein the top of the upper section where the optical center line passesthrough the turret.

[0117] In the exemplary embodiment, the connecting brace is cast as aloose piece and is then bolted to bosses that are integrally cast at theupper and lower portions of the basic “C” frame. The connecting brace ispreferably cast of the same material as the rest of the microscopeframe, so that it has the same thermal expansion and contractioncharacteristics. In the exemplary embodiment, this material is analuminum alloy. Alternatively, the brace could be cast as an integralpart of some or all other portions of the microscope frame.

[0118] Dual Plate

[0119] As described above, with respect to FIG. 3B for instance, themicroscope system of an exemplary embodiment may include a Z-axis plate13 from which three guideposts 55 extend into interference fit withbushings 54 that are attached to base 12. This arrangement provides forincreased stability and accurate vertical movement of stage 27. However,if the guideposts are rigidly fixed only to the underside of the Z-axisplate, there is still a possibility that the structure might sway undersome conditions. Moreover, if the elevating screw is in direct contactto the underside of the Z-axis plate, movement in the lateral directionis possible. Specifically, while the elevating screw is designed todirect force in the z-direction, unwanted force in the x- and/ory-direction is possible due to misalignment of the elevating screw.

[0120] To help minimize this possibility, still another alternativearrangement can be provided, as illustrated in FIG. 9A. Referring toFIG. 9A, an additional plate 216 is provided, fixed rigidly to theguideposts 55 preferably underneath the bushings. This lower platefunctions to increase the stability and stiffness of the post and platestructure, effectively creating an open box out of arrangement, and isbelieved to increase stability significantly. As shown in FIGS. 9A and9B, the Z-axis plate 13 and the lower plate 216 are rigidly affixed toone another by guideposts 55 and by a spacer post 230. Ball bushings 54,which are affixed to the base 12, run in an interference mode with theguideposts 55. As shown in FIGS. 3A-C, the ball bushings 54 are placedbelow the Z-axis plate 13. For additional stability, additional ballbushings 54 are placed directly above the lower plate 216. In thelowermost setting of the Z-axis plate, the distance 236 between theupper ball bushings and the Z-axis plate is minimal. Likewise, in theuppermost setting of the Z-axis plate, the distance between the lowerball bushings and the lower plate is minimal. This is to increase thestability throughout the movement of the Z-axis plate.

[0121] The spacer post 230 is affixed to the Z-axis plate via a screw232 and affixed to the lower plate 216 by a press-fit in an opening 238in the lower plate 216. The spacer post 230 is positioned directly abovethe elevating screw 89, with a nub 234 on the top of the elevating screw89 fitting in the lower portion of the spacer post 230. The spacer post230 serves two functions. First, it increases the rigidity of the entireZ-axis plate/lower plate structure, thereby improving its dynamicstiffness. Second, it serves as a rigid structure which may translatethe upward/downward movement of the elevating screw 89 to the Z-axisplate 13 and keep the Z-axis plate 13 parallel to the lower plate 216.In a previously described embodiment, the elevating screw 89 is incontact with one of the guideposts 55 (as shown in FIGS. 3A and 3B) sothat the upward force of the elevating screw is translated through theguidepost to the Z-axis plate 13. However, the current design allows foradditional stability since the spacer post 230 is rigidly affixed atboth of its ends (as opposed to the previous design which rigidlyaffixed the guidepost at only one end). In a preferred embodiment, asingle spacer post is used. In an alternate embodiment, a plurality ofspacer posts may be placed in between the Z-axis plate 13 and the lowerplate 216.

[0122] As discussed previously, the elevating screw 89 may have unwantedmovement in the lateral direction. Because it is very difficult to makethe elevating screw micron perfect (i.e., eliminating the lateralmovement in the elevating screw 89), the present design minimizes itseffects on the examination of the sample. The present design includescontacting the elevating screw with the lower plate rather than theZ-axis plate 13. Therefore, any lateral movement is felt by the lowerplate 216 but not translated to the Z-axis plate 13. Specifically,because of the rigidity of the Z-axis plate/lower plate structure andbecause of the guideposts 55 and ball bushings 54, the lateral movementis not translated to the Z-axis plate 13 (upon which the sample sits andwhere focusing is performed). Thus, the current design allows forincreased stability.

[0123] The lower plate 216 is “C” shaped and composed of the samematerial as the Z-axis plate 13. The shape of the lower plate is 216 isdictated by the optical path in the microscope system. The light travelsfrom the light source, though the open side portion of the “C” shapedlower plate 216, and reflected upward through the Z-axis plate 13.Moreover, as discussed previously, the guideposts 55 are affixed to theZ-axis plate 13 by an adhesive. In a preferred embodiment, theguideposts 55 are affixed to the lower plate 216 via collars 228. Thecollars 228, as shown in FIG. 9C, have a guidepost opening 240, a slit242 and screw openings 243. The collars 238 are affixed to the undersideof the lower plate 216 by slipping the collars 228 through theguideposts 55 via the guidepost opening 240, placing a screw 244 throughthe slit 242 of the collars (to hold the collars securely to theguideposts 55), and placing screws 246 through the collar (to hold thecollar to the underside of the lower plate 216).

[0124] Referring to FIG. 10, there is shown an apparatus for providingupward and downward force. Similar to the elevating screw shown in FIGS.2A and 3B, the apparatus includes a pulley which engages the top portionof a nut. The nut 87, via a collar 250, is in contact with the innerrace of radial bearings 57. The outer race of the radial bearings 57 isin contact with the base 12 (so that the outer race does not move). Thenut 87 contacts the elevating screw 89 via ball bearings 248. Duringoperation, the pulley 61 exerts force on the nut 87 thereby turning thenut 87. Because of the radial ball bearings 57, the nut 87 does not moveupward/downward. The radial movement of the nut 87 is translated into anupward/downward movement of the elevating screw 89. For additionalstability, thrust bearings 252 are added at the lower portion of theapparatus. The inner portion of the thrust bearings 252 is in contactwith the collar 250 and the outer portion is in contact with the base 12(so that the outer portion does not move). The thrust bearings 252complement the column design of the z-axis elevating screw drive, makingthe drive less compressible and stabilizing the drive in the thrustdirection. Thus, through the use of the radial bearings 57 and thethrust bearings 252, the nut is more secure during movement, so that theelevating screw is likewise more secure.

[0125] Rotating Wheel

[0126] As described above, the microscope system includes a lamp forilluminating the sample. Specific frequencies of illumination aredesired depending on the operation of the microscope. In order to filterout the unwanted frequencies, a motorized rotating filter wheelmechanism 254 is designed into the microscope frame. This mechanism 254is located in the illumination system path just after the lamp collectorlens and heat shield system, as shown in FIG. 11A. It is positionedbefore the field iris diaphragm. Locating the filter mechanism in thislocation has the following benefit of illuminating the specimen withonly the specific wavelength light desired and not the broad spectrum.This has certain advantages in some forms of the quantifiable imagingsystems. An additional benefit is the reduction in the amount ofvibrations. Because the filter mechanism uses a motor as the primemover, the vibrations caused by the motor and the moving mass do nothave a negative effect on the stability of the camera system. Becausethe motorized rotating filter wheel is (1) located far from the camera(relative to other components in the microscope) and (2) in the basecomponent, the most stable component of the system, so that the wheeldoes not appreciably affect the operation of the camera. In oneembodiment, the rotating wheel has 6 slots 256, as shown in FIG. 11B.The wheel 254 rotates so that filters placed in the slots 256 modify thespectrum of light in the optical path.

[0127] An exemplary embodiment of the present invention has beendescribed herein. It is to be understood, of course, that changes andmodifications may be made in the embodiment without departing from thetrue scope and spirit of the present invention, as defined by theappended claims.

I claim:
 1. A microscope system comprising, in combination: a baseportion extending from a front end to a back end; an upper portionextending from a front end to a back end; a back support extending fromthe back end of the base portion to the back end\ of the upper portionand providing rigid support of the back end of the upper portion inrelation to the back end of the base portion; a stage for supporting aspecimen, the stage being movable in relation to the base portion, theupper portion and the back support; a brace rigidly connecting the frontend of the base portion to the front end of the upper portion; and anoptical element mounted on the upper portion between the back supportand the brace.